Process and apparatus for oil shale retorting

ABSTRACT

A process and apparatus are disclosed for the continuous steady state retorting of ground oil shale in the absence of air. Retorting is accomplished by countercurrently contacting heated spent oil shale with fresh ground oil shale in a vessel from which air is excluded. The spent oil shale is heated by combustion of its carbonaceous residue to form a hot heat transfer medium which, when contacted with fresh oil shale in the retorting process, provides the energy for the recovery of hydrocarbons.

United States Patent 1191 Frick Jan. 8, 1974 [54] PROCESS AND APPARATUS FOR OIL 3,167,494 1/1965 Crawford 208/11 SHALE RETORTING 3,565,751 2/ 1971 Hoekstra....

3,617,466 11/1971 Todd 208/11 Inventor: George W. Fric k, Mercerville, NJ.

Primary Examiner-Curtis R. Davis AttorneyEdwin T. Yates Assignee: Cities Service Research &

Development Company, Cranbury, NJ.

Filed: Feb. 25, 1971 Appl. No: 118,795

[57] ABSTRACT A process and apparatus are disclosed for the continusence of air. Retorting is accomplished by countercur- 208/1l1200g2/l2/(2); yd i z g l fp k withl g z t groun 0i S ale in a vesse mm W ic a is exc u e I [58] Fleld of Search 208/1 1, 202/221 The spent oil shale is heated y Combustion of its I 56] References Cited bonaceous residue to form a hot heat transfer medium Y which, when contacted with fresh oil shale inthe re- UNITED STATES PATENTS torting process, provides the energy for the recovery 3,573,197 3/1971 Gessner 208/11 of hydrocarbons, I 3,597,347 8/197 1 Ellington.... 208/1 1 v 3,093,571 6/1963 Fish et a1. 208/1 1 10 Claims, 1 Drawing Figure CONDENSER INERT GAS FUEL GAS NAPHTHA a: E O O 20 g E O O: ,2 O 11: LL KEROSENE RECOVERY 2X (/1 AIR ,1. g BLOWER FUEL 35 1 OIL '8 g E 48 BLOWER PAIE I I IIII 8 I874 3; 784.462

(D CONUENSg 42B 5 E INERT GAS 4Q SEPARATOR 2 3?) FUEL GAS STACK HEAVY L oIL \f 3 GAS 2| 54 a: 4 37 E I 0: E;

i 39 I 2 l 8 DISTRIBUTOR 27 I Ag I i, NAPHTHA g 28 i CLElgHNG g a: 23 5 22 i 29 E @2 KEROSENE 30 SPENT I9 E SHALE TO MINERAL /46 RECOVERY FLUE GAS -49 BOILER 0) AIR L BLO;NER FUEL OIL i E 48 GAS BLOWER GEORGE w. FRICK,

INVENTOR.

ATTORNEY 1 PROCESS AND APPARATUS FOR OIL SHALE RETORTING BACKGROUND OF THE INVENTION This invention relates to a process and apparatus for the recovery of hydrocarbons from oil shale. More par ticularly, the present inventionis directed towardthe retortingof oil shale through use of spent oil shale as a heat exchangernedium.

Vast deposits of oil shale are located within the United States and are generally disposed beneath the oil, which is a hydrocarbon product much like crudeoil or petroleum and which may be processed to provide fuels and other useful products. Generally, a ton of oil shalecan provide 1 to 50 gallons of shale oil. Therefore, these vast depositsof oil shale provide a significant reserve of hydrocarbon materials from which energy may be derived. Economical production of hydrocarbons from the oil shale deposits could provide a tremendous contribution to this countrys national wealth and a great supply of hydrocarbon materials and energy.

Conventionally utilized and presently known oil shale retorting processes suffer from one or more disadvantages:

a. The retorting process is a non-steady state process with alteringconditions whichlead to control diffrculties and high labor costs.

b. The retorting is accomplished in the presence of air which degrades the oil product by producing.

oxygenated compounds which are not as useful as 'the hydrocarbon materials from which they were produced.

c. The disposal of spent'oil shale remaining after the retortingprocess. Residual carbonaceous material (coke) in thespent'shale leads to disposal problems and represents wasted potential energy.

d. Recovery of valuable minerals, such as sodium and aluminum, from spent oil shale with the high coke residue content is troublesome.

A problem whichis particular to the retorting process is the tremendous amount of heat required in order to retort or destructively distill the shale oil'from the minerals. In conventionalprocessing, heat isoften supplied by a medium such as hot gas or ceramic balls. This mode of heat addition increases investment and operating expenses in the process. Conventional processes are also sensitive to oil shale particle size distribution and require expensive classification equipment to provide shale feedstock with a proper. consistency. What is required is a method of optimumly heating and destructively distilling the oil shale for the economic recovery of hydrocarbons therefrom and for the optimum utilization of the heat expended in the retorting process.

It is an object of the present invention to provide a process and apparatus for the retorting of oil shale.

It is a further object of the present invention to provide a means for supplying heat through the utilization of spent oil shale.

It is still a further object of the present invention to optimumly utilize the heat generated during the retorting process, while simultaneously providing an easily disposable spent oil shale product and a waste flue gas free of polluting contaminants.

With these and otherobjects in mind, thepresent invention may be more fully understood through the following drawing and descriptionr.

SUMMARY OF THE INVENTION The objects of the present invention are accomplished through useof aproc ess of retorting hydrocarbons fromoil shale in a retorting vessel in which the oil shale is subjected to destructive distillation by the addition of heat in the substantial absence of oxygen. The improvement in the retorting process comprises the heat for the process beingadded through the continuousintroduction of heated spent oil shale as the heating medium. Generally, the spent oil shale is heated by combustion of its carbonaceous residue. Retorting is then accomplished by comingling'with fresh oil shale in a retortingvessel. It is preferred that the comingling be accomplished through the counter-current introduc tion of fresh oil shale into the. retorting vessel. The combustion of the spent oil shale may be achieved by contacting the spent oilshale with air to form hot flue gases and heated spent oil shale. The heat content of the hot flue gases produced may be recovered for further economic benefit.

Theobjects of the present invention may also be accomplished through apparatus for the retorting of oil shalecomprising a retorting vessel having a-hydrocarbon discharge and spent oil shale discharge. A hydrocarbon fractionator is connected to the hydrocarbon discharge of the retorting vessel for recovery of the hydrocarbon materials therefrom and means for introducing hot spent oil shale into the retorting vessel are provided. The means for introducing hzeated spent oil shale may comprise removing the spent oil shale from the discharge of the retorting vessel and passing it through a combustor, coupledwith means responsive to the temperature of the retorting vessel for introducing heated spent oil shale from the combustor into the retorting vessel.

The means for introducing spent oil shale into the combustor may comprise an inert gas lifter connected to the spent oil shale discharge of the retorting vessel and a spent oil shale disengager, fed spent oil shale by the gas lifter, connected to the combustor. Various mechanical means of lifting spent shale may also be employed. It is also preferred that a vapor condenser be connected to the disengager to receive the inert lift gas and any condensable, normally liquid compounds contained therein. These liquids are further separated in a gas-liquid separator connected to the condenser to recover the normally liquid compounds from the inert lift gas. In conjunction with the combustor may be means for purging heated spent oil shale from the combustor and means for reclaiming heat from the hot flue gases produced within the combustor.

BRIEF DESCRIPTION OF THE DRAWING The process and apparatus of the present invention may be more fully understood by referral to the accompanying FIGURE in which is depicted one embodiment of the oil shale retorting apparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method and apparatus which has been devised for the continuoussteady state retorting of ground oil shale in the substantial absence of air. Through the judicious selection of processing equipment, the retorting system iscapable of producing clean, high quality oil products, clean flue gas and spent oil shalecompletely free of carbonaceous materials. Through the oil shale retorting process of the present invention, steady state conditions are maintained in applying retorting heat by means of a circulating stream of heated spent oilshale. Retorting is accomplished through the intimate contacting of heated spent oil shale and fresh ground oil shale in a retorting'vessel from which air is excluded. Spent oil shale is heated by combustion of its carbonaceous residue in a reaction vessel called a combustor. It is generally found that spent oil shale contains a high content of residue or coke which is an unavoidable consequence of air-free retorting required for destructive distillation of the hydrocarbons from the oil shale. This residue is utilized to heat the spent oil shale into a heated or hot spent oil shale which may be utilized to supply the heating medium for the processing of the fresh oil shale supplied to the retorting vessel. Therefore, through use of the present invention, one avoids the environmental hazards of expending an effluent from the retorting vessel containing a coke residue which is undesirable and not easily disposed of through the consumption and utilization of the energy content of the'carbonaceous residue. Spent oil shale is continually withdrawn from the combustor in order to maintain a constant circulating inventory of spent oil shale in the system such that only a partial recycle of the spent oil shale occurs with constant purging of spent oil shale from the combustor in a clean, discardable or readily usable form for extraction of minerals therefrom for use in other processes.

Accordingly, with the'apparatus and process of the present invention, fresh oil shale is continuously introduced into the retorting vessel. The oil shale is subjected to destructive distillation by the addition of heat in the substantial absence of oxygen, with the improve ment of the present invention comprising the heating medium of the process being provided through the ad- 'dition of heated spent oil shale. The spent oil shale, heated by combustion of carbonaceous residue, is comingled with the fresh oil shale introduced into the retorting vessel. Generally, the comingling is accomplished by the counter-current introduction of fresh oil shale to the introduction of heated spent oil shale so that the most concentrated heat content of the heated spent oil shale contacts the hottest portion of the fresh oil shale introduced into the retorting vessel with an economic destructive distillation process being provided.

The apparatus and process of the present invention may be more fully understood by referral to the accompanying FIGURE. Fresh ground oil shale 11 is introduced continuously into an insert ,vessel 14 contained within a retorting vessel 13 by means of a screw feeder 12, although other possibilities for fresh oil shale introduction exist. For example, use ofa lock hopper or introduction by pumping a slurry consisting of ground shale mixed with a heavy oil into the retorting vessel 13 would accomplish the same end. The retorting vessel 13 can operate at or near atmospheric pressure, thus facilitating continuous fresh oil shale input. Heated spent shale flows in through a downward tangential entry point by means of an inlet pipe 22. Fresh oil shale is introduced into the incoming heated spent oil shale countercurrently to promote turbulent mixing and favorable heat transfer of energy from the heated spent oil shale to the fresh oil shale. The retorting bed level maintained in the insert vessel l4 by means of a notched circular overflow weir forming the top of the insert vessel 14. Bed temperature is automatically controlled by regulation of the inlet valve 23. Inlet valve 23 is controlled by a temperature controller 24, tempera ture responsive to the temperature of the oil shale within insert vessel 14. In general, retorting temperature will be controlled between 500 and l,500 F and preferably between 800 and 1,200 F depending on yield, structure of the apparatus, and the oil products desired. Higher temperatures will promote cracking of the shale oil and increasing yields of gas and light ends, while lower temperatures will increase the fuel oil and kerosene yields. The hydrocarbon vapors leave the retorting vessel 13 through stacks 15, having cyclone inlets to retain the oil shale fines within retorting vessel 13, and pass through a pipe 16 to a fractionator 17. The fractionator 17 consists of a multi-plate fractionation column which separates the retorted products into the desired boiling range materials, for example fuel oil 18, representing the bottoms of the fractionator l7, kerosene l9, naphtha 20, and fuel gas 21.

In order to maintain smooth circulation of spent oil shale, it is desirable to lift the spent oil shale particles leaving the retorting vessel 13. It is also economically desirable to remove as much heavy oil from the spent oil shale as possible before combusting the carbonaceous residue or hydrocarbon material remaining therein by the further heating of the spent oil shale. Both these requirements may be accomplished by blowing the spent oil shale upward with a fast moving inert lift gas preferably heated, through a vertical pipe. This is depicted in the FIGURE by a discharge line 44, discharging spent oil shale from retorting vessel 13 into an inert lift gas 47, provided by a gas blower 45. The spent oil shale and inert lift gas 47 pass through a riser pipe 46. Preferred lift gases include flue gas and steam, but inherently an inert gas should beutilized. The riser pipe 46 terminates at a disengager vessel 43 which serves toseparate the lift gas, through stacks 42, also having cyclones therein to retain fines. The lift gas passes through line 51 and is introduced into a condenser 52, which may be water or air cooled to condense the normally Iiquid components of the gas, for example, any heavy oils. The gas-liquid mixture is then passed to a separator 53 in which heavy oil 54 is separated therefrom. Spent oil shale forms a level 41 in the bottom of the disengager vessel 43. This material is then fed to a combustor 26 to form a level of spent oil shale 25 therein. The level of spent oil shale 41 in the disengager 43 is regulated by a level controller 40 connected to a responsive valve 39 connected within the discharge tube 38, from the disengager vessel 43, which feeds spent oil shale to the combustor 26.

The hot bed of shale particles is maintained in the combustor 26 by continuously buring the coke contained within the spent oil shale with air 48 blown into the bottom of the combustor 26. The air 48 is introduced through an air blower 49 and air line 50, and passed through a distributor plate 27 to uniformly heat and combust the carbonaceous residue contained within the spent oil shale bed 25. The distributor 27 may consist of a perforated grid or a network of pipes having holes at close intervals. Spent oil shale flows in y from the disengager 43 through the discharge pipe 38 in a downward tangential entry which promotes turbulent mixing with air 48 introduced into the combustor 26, resulting in complete combustion of the carbonaceous residue of the spent oil shale. Heated spent oil shale is introduced into the retorting vessel 13 through an overflow well comprising the inlet pipe 22 extending within the retorting vessel 13 and is controlled by temperature control 24 previously disclosed. in addition, excess heated spent shale oil is. continually withdrawn from the combustor 26 by the use of a level control 31 having a responsive valve 29 connected to a discharge line 28 such that spent oil shale 30 is provided for mineral recovery and/or disposal as it is continually purged from the combustor 26.

As it would be possible to produce a totally carbon free spent oil shale by contacting the excess spent oil shale withdrawal stream with oxygen, a totally clean spent oil shale may be produced from the apparatus of the present invention for total environmental control and no adverse pollution effects. The process, therefore, is not inhibited by pollution criteria.

Flue gas which is vented through stack 34 and line 32 from the combustor 26 is passed through the cyclones contained within stacks 34, to remove fines, and

heat boiler 35 recovers combustion heat value not used in the retorting process. This further allows for mini-' mum waste of oil shale energy potential. Cool flue gas, leaving the waste heat boiler 35, may be subjected to various gas treating operations for removal of particulates and pollutants such as S0 by passing the flue gas through stack gas cleaning stage 36. The clean flue gas produced is then sent through stack 37 into the atmosphere. Therefore, through the process of the present invention, production of clean flue gas and clean spent oil shale insures minimum environmental debasement. As the combustor 26 may be operated in the range of 800 to 2,000 E, the assurance of complete combustion of carbonaceous materials and with the absence of conventionally produced carbonaceous residues normally associated with spent oil shale removed, environmental control and reclamation of any heat content or energy value contained within the oil shale is provided.

Accordingly, by use of the apparatus and process of the present invention, oil shale is heated by the combustion of its own carbonaceous residue through a process whereby steady state conditions are maintained in supplying retort heat by means of a recirculating preciated by those in the art that various changes and modifications can be made therein without departing from the scope of the invention as set forth.

Therefore, I claim:

1. In a process for the retorting of hydrocarbons from oil shale in a retorting vessel in which the oil shale is subjected to destructive distillation by the addition of heat in the substantial absence of oxygen, the improvement which comprises the heat for the process being added through the introduction of heated spent oil shale.

2. The process of claim 1 in which:

a. the spent oil shale is heated by combustion of its carbonaceous residue, and

b. the heated spent oil shale is comingled with fresh oil shale in the retorting vessel.

3. The process of claim 2 in which the comingling is accomplished through introduction of the heated spent oil shale countercurrent to the introduction of fresh oil shale.

4. The processof claim 3 in which the combustion of the spent oil shale is achieved by contacting the spent oil shale with air to form hot flue gases and heated spent oil shale.

5. The process of claim 4 further comprising recovering the heat content of the hot flue gases.

6. Apparatus for the retorting ofoil shale comprising:

a. a retorting vessel having a hydrocarbon discharge and spent oil shale discharge;

b. a hydrocarbon fractionator connected to the hydrocarbon discharge of the retorting vessel; and

c. means for introducing heated spent oil shale into the retorting vessel.

7. The apparatus of claim 6 wherein the means for introducing hot spent oil shale comprise:

a. a spent oil shale combustor;

b. means for introducing spent oil shale from the spent oil shale discharge of the retorting vessel into the combustor; and

c. means responsive to the temperature of the retorting vessel for introducing heated spent oil shale into the retorting vessel.

8. The apparatus of claim 7 in which the means for introducing spent oil shale into the combustor comprise:

a. an inert gas lifter connected to the spent oil shale discharge of the retorting vessel; and

b. a spent oil shale disengager, connected to the combustor, fed spent oil shale by the inert gas lifter.

9. The apparatus of claim 8 further comprising:

a. a vapor condenser connected to the disengager to receive the inert lift gas and condense normally liquid compounds contained therein; and

b. a gas-liquid separator connected to the condenser to separate the normally liquid compounds from the inert gas.

10. The apparatus of claim 7 further comprising:

a. means for purging hot spent oil shale from the combustor; and I b. means for reclaiming heat from the hot flue gases produced in the combustor. 

2. The process of claim 1 in which: a. the spent oil shale is heated by combustion of its carbonaceous residue, and b. the heated spent oil shale is comingled with fresh oil shale in the retorting vessel.
 3. The process of claim 2 in which the comingling is accomplished through introduction of the heated spent oil shale countercurrent to the introduction of fresh oil shale.
 4. The process of claim 3 in which the combustion of the spent oil shale is achieved by contacting the spent oil shale with air to form hot flue gases and heated spent oil shale.
 5. The process of claim 4 further comprising recovering the heat content of the hot flue gases.
 6. Apparatus for the retorting of oil shale comprising: a. a retorting vessel having a hydrocarbon discharge and spent oil shale discharge; b. a hydrocarbon fractionator connected to the hydrocarbon discharge of the retorting vessel; and c. means for introducing heated spent oil shale into the retorting vessel.
 7. The apparatus of claim 6 wherein the means for introducing hot spent oil shale comprise: a. a spent oil shale combustor; b. means for introducing spent oil shale from the spent oil shale discharge of the retorting vessel into the combustor; and c. means responsive to the temperature of the retorting vessel for introducing heated spent oil shale into the retorting vessel.
 8. The apparatus of claim 7 in which the means for introducing spent oil shale into the combustor comprise: a. an inert gas lifter connected to the spent oil shale discharge of the retorting vessel; and b. a spent oil shale disengager, connected to the combustor, fed spent oil shale by the inert gas lifter.
 9. The apparatus of claim 8 further comprising: a. a vapor condenser connected to the disengager to receive the inert lift gas and condense normally liquid compounds contained therein; and b. a gas-liquid separator connected to the condenser to separate the normally liquid compounds from the inert gas.
 10. The apparatus of claim 7 further comprising: a. means for purging hot spent oil shale from the combustor; and b. means for reclaiming heat from the hot flue gases produced in the combustor. 